Nozzle



Jan. 29, 1952 J, CHALOM 2,583,726

NOZZLE Filed Jan. 17, 1949 A 3 ll m 3 v v 1 2 A Ff 3 B h 744 Di 45 \C Fig.5

Patented Jan. 29, 1952 NOZZLE Joseph Aaron Chalom, Paris, France Application January 17, 1949, Serial No. 71,33 In France January 26, 1948 4 Claims. (Cl. 51-282) This invention relates to nozzles for the expansion and compression of gases and vapors, such as for instance the nozzles of supersonic electors.

. It has for one of its objects to provide nozzles of the kind indicated above, in which the losses of energy are reduced to a minimum.

It is another object of this invention to provide a novel way of making such nozzles in a simpler, quicker and less expensive way than was hitherto possible, and which results in nozzles having particularly favorable properties.

The invention is based on the following findings: If a gas jet carrying sharp and abrasive particles such as sand grains is injected into a cylindrical bore, for instance by replacing the nozzle of a sand blast apparatus by a metal piece formed with a cylindrical bore, it will be found that there is quickly formed a hollow revolution surface with a concave profile facing the axis and which at a certain distance from the entrance of the bore attains a maximum diameter which merges into contracted and expanded sections. The length of the bore and its diameter determine, all other factors remaining constant, the diameter at each point and the distance from the entrance at which the largest diameter hollow is situated.

If the hollowed-out piece is cut through at the largest diameter, there is obtained a nozzle,

the profile of which is concave toward the axis and is joined by means of an angular profile in its narrowest section with a rounded part of a minimum diameter only a little greater than that of the initial bore. A concave profile of this kind enables the streams of fiuid expanded at maximiun speed at the maximum section to travel in parallel and thus to reduce the shocks to a minimum.

At the neck of the nozzle where thecross-section is the lowest, while the speed of the fluid comes closest to the velocity of sound, the profiles are joined along an angular profil with a tangent angle at the maximum ranging between and degrees. This type of profile, obtained by the automatic hollowing of the piece by a sand blast or the like differs definitely from the customary profiles in which as a rule opening cones of only about 7 degrees are used.

The new profile of far more rapid evolution leads to shorter nozzles, which is advantageous. By making use of these facts, and by systematic experimenting it becomes possible to calculate the elements of diameter and length of the bore i e Obtained inpredetermined cases.

z The production of such: a profile and its applications are illustrated diagrammatically by way of example in the drawings aflixed to this specification and forming part thereof.

. In the drawings Fig. l is an axial section of a nozzle blank designed to be subjected to the hollowing-out treatment according to the invention.

Fig. 2 is a similar view of a blank fitted with an auxiliary piece before being treated.

Fig. 3 is the finished nozzle.

Fig. 4 is an axial section of an ejector fitted with an expansion and a super-sonic compression nozzle.

Fig. 5 illustrates the adaptation of the concave profile according to the invention to a multistage nozzle.

Fig. 6 shows a blank for the production of subsonic nozzles according to the invention by means of a modified treatment according to the invention, and

Fig. 7 shows a compression nozzle in which a super-sonic element of concave profile is combined with a sub-sonic expansion nozzle produced in accordance with the invention.

Referring to the drawings and first to Figs. 1 and 2, Fig. 1 shows a blank A of dimensions approximately calculated for the nozzle to be produced, being a cylinder I with threaded endpieces 2 and 3 of smaller diameter which serve for the provisional and the permanent mounting in place of the blank and the finished nozzle, respectively. The two threaded endpieces might of course be replaced by some other fixation means. The thread 3 is so chosen that'the diameter at the bottom of the thread is equal to the diameter of the exhaust end of the nozzle to be produced. An auxiliary cylinder B of about equal length is screwed down on the endpiece 3 and the two united cylinders are now bored axially, the diameter of the bore being slightly smaller than the neck of the nozzle. The united pieces are then mounted by the threaded endpiece in the exhaust of a sand blower which is. now started running. The sand blast passing through the bore 4 hollows out the bore until the inner diameter of the bore in the end plane C of the body A becomes equal to the diameter of the endpiece 3. When this point is reached, the auxiliary cylinder drops and the blower is shut off. The body A is now hollowed out according to the profile 5, which is the one desired, being concave towards the nozzle axis in its super-sonic section and having, in the sections corresponding to the highnozzles.

The end of each operation is indicated automatically by the dropping off of the auxiliary cylinder B. The nozzle A can then be finished by filing the outer edge of the exhaust end and bringing the diameter of the neck tothe exact measure required.

The ejector shown in Fig. 4 is formed with nozzles of concave profile serving for ejecting air or steam from condensers or other apparatus. Itcomprises a steam intake compartment H, a. s rson c expansi nozzle I2 with c cave. p ofi e, asuct on box I3 a su e -s ic om. n ess q z e. M. wi h concave pr fi e n sub-sonic diffuser L5,. The end of the nozzle 12 is beveled and placed somewhat to the inner side oi the intake end of the. nozzle 54.

Owing t0 their concavities, facing the axis or the nozzles, the, profiles. according to the invention offer a great variety of inclinations towards the axis, starting from, a maximum at the. neck to their disappearance at, the. widest opening,

curves meet, being characterized by a double value of the angle of the tangent on that point, one being substantially zero, the other one for instance 10-15 degrees. The angle points which are thus obtained between a certain number of sections of a nozzle corresponding to a certain number of exhaust conditions, by favoring the separation of the gas currents from certain values of exhaust conditions. on, allow me to obtain, from the best adapted section on, parallel exhaust. This parallel exhaust flow then passes without any inconvenience through sections of allowing to obtain, by an association of, such i e n sr files, a g neralv profile wh ch present angle points with an angle of 10-15 degrees be.- we n. he an en s n these po nt omm n to two profiles. This, is, in direct contrast to the conventional profiles hitherto used which allowed only minute. ch nges. of. n ination between two profiles which were themselves little inclined an l c ny aluable ncl at ons.- Obviously this is an important result of the use of concave profil s a cord n til 1h? nve tion.

If. a noz le is 0 instan use for a pa sion of steam to a predetermined lower pressure, it is known that, if this. pressure rises, while all larger diameter which have not much to do with the functioning of the nozzle. The figure shows schematically such an operation under conditions arising between the maximum pressure dropcorresponding to the first element alone and the minimum pressure drop corresponding to the entire nozzle. This solution was not possible with the conical profiles of low angle apex in which one would have been limited to an insignificant change of angles The solution thus results directly from the type of profile obtained by the method of fabrication according to this invention; Fig. 5 illustrates diagrammatically the expansion nozzle of a steam ejector, according to the invention, in which the parts of which it is composed, are assembled by means of screwthreaded sections machined as perfectly as possible so that the adjoining profiles merge into one another as perfectly as. possible. The number of parts is a function offthe range of aspiration pressures to be obtained, but it may also be dictated, by the machining facilities; available. Experience, has shown that if the maximum section, exceeds four times the minimum section, the period of time required for machining the profile of the nozzles byway of sandblasting as indicated above, be gins to become prohibitive. It is therefore. advisable to compose. the nozzle of the number of 7 pieces which is closest to the quotient. by' 4 relother conditions, remain unchanged, the adhesion of the steam jeilto the. wall. will, cause the expansion to be lowered to a value which may be very muchlower than the pressure, which then obtains efiectively, and that, this expansion will i b follow d by a. sud n r compr s i nv y Shock wave, all this resulting in considerable losses of n t c. energy Sin e indu rial a p ratus sfi d with expans onno zle must. be able. o iu on under mpre 01'. le s consid rable chan es; Qty-19 ns c ndi tions, suc nozz e ate. as ru e. made s ort r than the length theoretically corresponding to mean conditions. However, if the loss of output suiiered by a rising of the expansion pressure above these conditions is avoided there exists another cause for losses. by the undulatory flow at the exhaust when the expansion pressure is curvature by abruptly varying thevalue of'the an e f he ansent at the p ofile relative to he o z ax s fro it m mum' al t i sim r im m value: Qne hus b a n a SQQntlnuQu profile composed; Q tw 0. morecurve openin toward the; axis, the. points whe e i ferent ative to the maximum and minimum sections. of the entire nozzle.

Obviously, since the method according to the invention produces a concave profile of a novel type, it might be, possible to, produce by less eco nomical machining methods of the classical kind nozzles which, might come near to the prof11esaccording to the invention, no matter whether the profile is simple orgas explained above, composed of a series of concave elements succeeding each other by definite angle, points, corresponding at th par lel. xh t t th axis. f a pr file extended by the adjoining part, open at 20-30 degrees; ft-he next oll s p file...

: Without departing from; the invention, it is also possible to utilize modified, forms of proceeding for the production of'rather, short concave profiles, for which the method according to the invention furnishes automatically the profiles with continuously varying curvature as explained above, which are. useful for super-sonicjexpansion period] has been establishedfby tests, it will be sufficient to stop the sandblastat. the. end, of this period. Theconcaveprofile withpara elgas itnout exhaust is then obtained againand a'ga the necessity of a drop of material as in the modification first described.

On the other hand the method according to this invention, by facilitating the hollowing out of the blanks, enables long profiles corresponding to sub-sonic velocities to be fabricated automatically. To this end a blank of the desired length may be pierced, not by a cylindrical bore, but by a hollow constituted by a plurality of coaxial cylindrical bores T1, T2, T3 (Fig. 6) of increasing diameters which succeed one another within the central section of the blank. The length L1, L2, L3 and the diameters of these cylindrical borings will be determined by tests or empirically.

Under these conditions there is obtained with the aid of the grinding blast a continuous oblong profile which closely follows the desired profile C, and by synchronization or by any other means announcing the end of the fabricating period, oblong sub-sonic profiles can be produced.

By combining, as shown in Fig. 7, a super-sonic difiuser F of concave profile with a sub-sonic diffuser E of oblong profile, a diffuser is obtained which will be capable of compressing a flowing gas from super-sonic velocities down to a velocity approaching zero.

The new method can be carried through with the aid of any suitable fluid, besides compressed air, for instance steam, and with any other suitable abrasive matter, besides sand. The form of the jet may be changed during operation, for instance near the end.

Various changes may be made in the performance of this invention and in the means employed for this purpose without departing from the invention or sacrificing the advantages thereof.

I claim:

1. The method of machining the cylindrical inner surface of blanks of pressure-fluid nozzles for the production of an optimal profile for subsonic flow in the intake section and for supersonic flow in the exhaust section of the nozzle, which comprises acting with an axially directed jet of gas laden with particles of abrasive matter on the cylindrical inner blank surface, until a cavity is formed, in which the angle between the nozzle axis and the tangent to the inner nozzle surface, which at the narrow throat in which the subsonic and the supersonic sections meet, is

substantially zero, at the entrance to the supersonic section abruptly rises to 10-15 degrees, to then drop continuously in the direction of exhaust and becoming zero at the exhaust end.

2. The method of claim 1, in which a blank is treated having a cylindrical bore of a diameter slightly inferior to the diameter desired at the nozzle neck, said blank being formed, at a distance from the neck and determined by experiment, with a screw-threaded extension of a diameter, at the bottom of the thread, equal to the maximum diameter of the inner bore of the nozzle desired, another blank of about equal length being screwed on said threaded extension, this other blank, by its drop when the main blank hollow has been finished, indicating the end of the operation.

3. The method of claim 1, in which a blank is treated which is pierced by a cylindrical bore of a diameter slightly inferior to the diameter desired of the nozzle neck and of about the same length as the nozzle bore to be produced, the dimensions of the nozzle and the period of time required to hollow it out being first ascertained by tests to enable successive operations to be timed accordingly.

4. The method of claim 1, if applied to the machining of nozzles of oblong sub-sonic profile, in which a blank is treated which is pierced by a series of coaxial bores of increasing diameter distributed in accordance with a profile substantially coinciding with the profile to be produced.

JOSEPH AARON CHALOM.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,506,721 Gavorsky Aug. 26, 1924 1,506,722 Yunker Aug. 26, 1924 2,196,169 Twombly Apr. 2, 1940 2,225,521 Holveck Dec. 17, 1940 2,318,769 Freeman et a1 May 11, 1943 2,371,533 McDougal Mar. 13, 1945 2,419,667 Luckey Apr. 29, 1947 FOREIGN PATENTS Number Country Date 392,826 Great Britain May 25, 1933 

